Can we go back to before time equals zero? What does that even mean?
A physicist explains why cosmology is the oldest science, how we know the age of the universe to within hours, and why the biggest questions in physics are also questions of philosophy.
This course covers the most fascinating aspects of all of cosmology! It's truly the most captivating journey through the cosmos imaginable; exploring its vastness, the tools used to unravel its mysteries, and the groundbreaking discoveries that have shaped our understanding of the universe.
We examine the evidence for an expanding universe, the forces driving its evolution, and the cosmic fossils that shed light on its distant past and future. We also explore the enigmatic concepts of dark matter and dark energy, their roles in the universe's structure and fate, and the ongoing efforts to unravel these cosmic mysteries.
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We are going to explore this universe together.
Cosmology is the oldest science known to humanity.
Since cavemen and women, people have wondered where did everything come from?
We're not going to do any alien autopsies or anything in this class,
but we are going to cover a lot of fascinating questions.
Where do we come from?
Where are we going?
What is the universe made of?
How can we possibly understand the grand landscape of the cosmos?
When you look back in space, you look back in time.
It's amazing we've been able to do this,
to study the properties of the cosmos.
Time scales of billions of years.
Size scales billions of times bigger than our own.
And now the question is, can we go back to time equals zero?
Can we go back to before time equals zero?
And what does that even mean?
I hope in this course to keep striving and asking these great questions,
because without great questions, there can be no great answers.
And without great answers, there can be no understanding.
Welcome, everybody.
It is a great pleasure to be here.
I've traveled literally trillions of micrometers
and billions of seconds to be here,
and we are going to explore this universe together.
And I hope it's going to be a fun trip.
It is going to take us back in time
and throughout the entire observable universe.
So I hope it's going to be quite interesting
and I hope there'll be a lot of good questions.
That is the best part of my job is answering questions.
So by way of background, I am a cosmologist,
not a cosmetologist, despite the look,
the hair and the makeup that they've done here.
But there is a similarity between those two words,
as you may have noticed.
And I often get asked for either tips on hair and makeup
or to read the zodiac sign of my guests,
neither of which I'll be doing.
But cosmology and cosmetology do share the same prefix, cosmos.
And there's a reason for that.
Because in Greek, cosmos means beautiful or appearance.
And the universe is incredibly beautiful.
And so it's not really such a surprise
that they should have this prefix in this relationship together.
But again, if you came expecting hair and makeup,
you're going to be disappointed.
What we are going to talk about
is what I call this cosmic circle.
Cosmic circle involves the universe and ends with us
and may begin again with us
as we strive to understand the universe
using very simple tools,
actually tools we're all born with.
There are two telescopes in our heads,
my favorite subject.
I hope to communicate some of the infectious questions
that we're all born with.
And it really takes formal education sometimes
to beat that curiosity out of us.
So I want to instill that curiosity back.
We're going to be really kind of involving very simple tools,
telescopes, computers, and brains.
Simple in some sense, very complicated in others.
We're going to ask how those tools help us gather evidence
and what that evidence can tell us
about the past history of the universe
and perhaps its deep future.
And more mesmerizingly than almost anything,
are there other universes?
And can we contact them?
And if we contacted them, what would that mean?
We're not going to do any alien autopsies
or anything in this class,
but we are going to cover a lot of fascinating questions.
I aim to do this with some equations, but not too many.
I cannot teach a class in cosmology
and not use the famous equation E equals MC squared.
You'll be encountering that
and understanding hopefully how it was derived
and what it means so that you may more effectively use it
when you are educating other people
about what you've learned in this class.
The grand scope of cosmology is perhaps best depicted
by where it fits in, at least in popular culture.
And the repository of all knowledge
is nowadays it's Wikipedia.
It used to be Encyclopedia Britannica when I was a kid,
but now it's Wikipedia.
And if you go to the page that says science,
you don't see biology, you don't see DNA strand,
you don't see a T-Rex skeleton,
all of which we will encounter in this class
in one form or another.
I'll explain why.
You see a picture of the evolution of the universe.
It's pretty surprising.
If this picture, if Wikipedia existed even 30 years ago
when I began my career,
this would have been completely unbelievable.
Why would you include cosmology?
For you see in that time in the 1990s,
the age of the universe wasn't known exactly.
It was thought to be at least 10 billion years old,
but it could be 20 billion years old.
Now, if you're young and someone says,
well, you're 10 years old, maybe it could be 20,
that sounds really good.
If you're something like my age or older,
you don't want to be overestimating that person's age.
So it was laughable that you'd even include cosmology
as what's called a precision science,
a scientific process by which we'd come to understand
and maybe even categorize and exemplify
the scientific method.
That was laughable.
Nowadays, we know the age of the universe
to within the equivalent of being able to look out
at any one of you in the audience and say,
I know within a few hours of when you were born,
not just your age, but the day, the month,
the day, the year, the hour.
So it's incredible how much we've come.
And I'll explain how that's happened
by way of the technology and tools
we will encounter in this class.
So this is what appears in Wikipedia.
And why is that?
We're going to cover by the end of this course,
you'll understand why cosmology features so centrally
in the description of modern science.
And we'll dig into this diagram that's provided from NASA
that shows our universe and its evolution
throughout cosmic history.
But it also makes predictions
about what's going to happen in the future
and what happened at the beginning of time
that surprisingly Wikipedia may have gotten wrong.
We want to understand what are the limitations
that led to the perhaps the flaws in this diagram.
So hopefully we can organize a letter writing campaign
and get that changed.
But what is cosmology?
I already said cosmos means beautiful or appearance,
but cosmology is the laws of physics
when applied to the universe as a whole.
The properties of our universe
are determined by the laws of physics.
We're going to encounter all four main laws of physics,
the law of electromagnetism, which governs light,
the law of gravity, which governs objects
and how they move.
And there are two nuclear forces that we'll encounter
when we talk about what the matter is in the universe
that we're made up of,
that everything we've ever encountered is made up of,
and what other types of mysterious matter
that may exist in the universe
that goes by the name of dark matter
and other forms of energy that are equally mysterious
called dark energy.
So by the end of this class,
you will understand the observational techniques,
the scientific data that have been collected
and how they've led to a model that's so precise and accurate.
And the distinction between those will become clearer
that it is the very hallmark of what science is.
And towards the end of the class,
we will start to encounter the biggest picture topics
in all of science.
How do we know what we know?
How can we make predictions that are based upon objects
that we can't even see, encounter?
We don't live long enough to experience
the full scope and grandeur of the universe.
And yet, and yet,
we can make fantastical predictions
based on our observations of the past
about what will happen in the future.
And then lastly, as I said a few moments ago,
a huge question,
perhaps the most interesting question,
not just in cosmology, my field,
but in all of science,
is the question of other universes.
And this will involve not just the question of physics,
not just even the laws
that we're not going to spend as much time on,
what's called quantum mechanics,
but it may involve bigger picture questions
than we even think of being associated
in a scientific course such as this.
Namely, questions of origins,
of fine tuning,
of a creator,
a philosophy,
of theology even.
Now this is not going to involve discussions of that,
but it's impossible to ignore them.
So we'll talk about that
in the context of other possible universes
and other life forms.
So I always say,
if you could only choose one class,
and I'm a pretty biased person in this regard,
but if you could only choose one class
to study in all of your higher education,
it would be cosmology.
That is the question we are going to chase
across this entire series.
Can we actually get to before time equals zero?
Next time we start with the ancient Greeks
and work our way to Einstein,
and I send a free weekly email
on exactly these kinds of questions.
Link is in the description.
